Vaccines can achieve herd immunity

A social media post (archived here) claims to explain how vaccines work and why they supposedly cannot achieve herd immunity. The author argues that the body reacts differently to natural infection versus vaccination, insisting that only natural contact with a virus can lead to strong immunity. The post doesn't specify any particular vaccine or illness, implying it refers to all vaccines.

The post, however, misrepresents how the body responds to vaccines and pathogens while overlooking the fact that different types of vaccines exist, each working in distinct ways. There are numerous examples demonstrating vaccines' success in controlling the spread of diseases and even eliminating them.

Research

According to the Association for Professionals in Infection Control and Epidemiology (APIC), herd immunity occurs when a high percentage of the community is immune to a disease (through vaccination and/or prior illness), making the spread of this disease from person to person unlikely. Even individuals not vaccinated, such as newborns and the immunocompromised, are offered some protection because the disease has little opportunity to spread within the community.

Vaccine expert Dr. Paul A. Offit, Director of the Vaccine Education Center at Children's Hospital of Philadelphia, explains that herd immunity works "like a moat around a castle. The more and more people you immunize, the more difficult it is for the virus or bacteria to spread."

We took a closer look at the misleading claims presented in this post, addressing them separately.

"The issue with vaccines is that they don't contain the wild strain of these illnesses. Instead, they use genetically modified or altered versions of the virus or bacteria."

In reality, there are several different types of vaccines. According to the U.S. Department of Health and Human Services, each type is designed to teach your immune system how to fight off certain kinds of germs — and the serious diseases they cause.

Live attenuated vaccines use weakened versions of the virus, which are not genetically modified but are altered to be less virulent (measles, mumps, rubella vaccines). Inactivated vaccines contain killed viruses or bacteria and are not genetically modified, as seen in the polio vaccine. Subunit, recombinant, or conjugate vaccines (Hepatitis B vaccine) use parts of the virus or bacteria (protein or sugar) or genetically engineered material. Still, these are not the whole wild virus or bacteria. mRNA vaccines, such as those for COVID-19, do not use the virus at all. They provide genetic instructions for cells to produce proteins that mimic parts of the virus, triggering an immune response.

While it is true that not all vaccines contain the wild strain, this is a deliberate method to ensure safety while still teaching the immune system to recognize and fight the real pathogen. 

"Vaccines typically trigger a TH2 response."

This is not true. Vaccines can trigger both TH1 and TH2 responses, depending on the type of vaccine and the pathogen it targets. 

As Jahnavi Konduru, an associate scientist at Abbott, a multinational medical devices and healthcare company, explained to Logically Facts, T helper cells are a type of lymphocyte that play an important role in the immune system. They activate other immune cells to fight off infection or disease. There are two main types of T helper cells: TH1 and TH2 cells, each with unique functions. 

TH1 cells promote responses that deal with intracellular pathogens, while Th2 cells are more involved in combating extracellular pathogens. This dual response leads to the production of memory B and T cells, ensuring that if the person is exposed to the same virus in the future, the immune system will recognize it quickly, preventing reinfection. This is why infections like measles, mumps, and chickenpox generally provide long-term or lifelong immunity after a single infection. Vaccines work by mimicking this natural process without causing the disease. 

Vaccines designed to protect against pathogens such as measles or tuberculosis (BCG vaccine) primarily stimulate a TH1 response, leading to cell-mediated immunity. Vaccines that primarily induce an antibody-mediated response, such as influenza vaccines, can trigger a stronger TH2 response. mRNA COVID-19 vaccines are designed to activate both TH1 and TH2 responses.

"Vaccines can prompt a quicker immune reaction, but it's dangerous AND they don't teach the immune system to remember how to fight the infection in the long term."

Vaccines are designed to train the immune system for quick and long-term protection. They specifically work by teaching the immune system to "remember" pathogens. Vaccines do this by stimulating the production of memory cells (B and T cells), which remain in the body for years, sometimes for life, depending on the vaccine. 

Vaccines undergo rigorous testing for safety and efficacy before being approved for public use. While vaccines can cause mild side effects like soreness or fever, serious side effects are extremely rare. The benefits of vaccination in preventing life-threatening diseases far outweigh the risks of severe side effects.

"True herd immunity is a natural process that can't be fully replicated through" vaccines.

While herd immunity can be achieved through natural immunity, acquired after recovering from an infection, it is not the only way to do so. Also, natural immunity can come at a high cost, as it requires many people to become infected, leading to potential illness, complications, and death. The World Health Organization considers attempts to reach herd immunity by exposing people to a virus "scientifically problematic and morally unethical."

Vaccination can and does replicate herd immunity effectively and more safely. Vaccinating a large portion of the population can dramatically reduce or even stop the spread of infectious diseases. For example, vaccines against measles, polio, and smallpox have successfully created herd immunity in many parts of the world, leading to the eradication of smallpox and the near-elimination of polio.

Dr. Gregory Poland, a head of the Mayo Clinic's Vaccine Research Group, told us, "Vaccines effectively train the immune system to develop immunity, which is crucial for protecting vulnerable populations." According to Dr. Poland, "Vaccines help prevent dangerous diseases by prompting a safe immune response, reducing the risk of severe illness or death without needing to contract the disease itself." 

Dr. Offit adds, "The price paid for immunity after natural infection might be pneumonia from chickenpox, intellectual disability from Haemophilus influenza type B (Hib), pneumonia from pneumococcus, birth defects from rubella, liver cancer from hepatitis B virus, or death from measles. Immunization with vaccines, like natural infections, typically induces long-lived immunity. But unlike natural infection, immunization does not extract such a high price for immunity."

The verdict

The claim that vaccines cannot contribute to herd immunity stems from a misunderstanding of how vaccines work. Vaccination is a safe and effective method to protect entire populations from infectious diseases. Achieving herd immunity through vaccines has been shown to save lives and curb disease spread without the dangers of natural infection.

Therefore, we have marked the claim as misleading.